How is it possible, incorrect keyboard assignments
Do you have multiple languages on your computer?  I ran into this b/c I also have French on my computer and whenever I pressed alt+something (I never figured out what I pressed) it would change languages and so the keyboard would change and so would the shortcuts.  The way to fix this is to minimize Blender, go on the taskbar, bottom right, and see if there is a different language select.  If so, you've found your problem, just click on it and change it back.  If not, IDK.